1. Field of the Invention
The present invention relates to an image display apparatus and, more particularly, to an image display apparatus in which a plurality of projection display apparatuses are combined together to form a large screen.
2. Description of the Background Art
A multi-vision system including an arrangement of a plurality of projection display apparatuses for projecting an image from a projection unit onto a screen is known in the prior art.
As shown, for example, in FIG. 1 and FIG. 2 of Japanese Patent Application Laid-Open No. 8-140024 (1996), the multi-vision system has a structure such that only a screen for forming and displaying an image thereon is not covered with a wall surface but is exposed to the outside and the remaining parts are provided so as to be embedded in the wall. For this reason, the multi-vision system operates in a half sealed condition.
Each of the individual projection display apparatuses has a structure such that a fan for air cooling of the interior of an enclosure is provided to exhaust heat to the outside, as illustrated, for example, in FIG. 1 of Japanese Patent Application Laid-Open No. 2001-343708. However, heat is exhausted to half closed space.
In general, space is often provided for maintenance on the rear side of the multi-vision system. However, when the process for efficiently exhausting heat is insufficient even if the space is provided or when the image display apparatus is of the type in which the maintenance is performed from the screen side, it is impossible to ensure an efficient heat exhaust structure because of the limited space in some cases. In such cases, heat exhausted from the individual projection display apparatuses is retained in the half closed space inside the walls because of the circulation of the heat therein. This gives rise to a situation in which sufficient cooling cannot be achieved by cooling mechanisms of the individual projection display apparatuses. In the case of the insufficient cooling, there is a likelihood that the quality of the image display apparatus is degraded by heat.
To take remedial steps, it is contemplated that a mechanism for compensating for the cooling capability of the image display apparatus is added by providing an air conditioner and the like in the half closed space inside the walls, whereby an air cooling system for the multi-vision system is provided. This, however, presents another problem in that the cost for the placement of the air conditioner and the extension of the period of construction result in increased costs.